Method of making shoe stiffeners



Patented Jan. 16, 1940 PATENT OFFICE 2,187,005 7 METHOD or MAKING snor.srmmnnas Richard Almy, Lancaster, Pa., assignor to Armstrong CorkCompany, Lancaster, Pa-., a corporation of Pennsylvania No Drawing.Application December 2, 1935, Serial No. 52,542

3 Claims.

This invention relates to a method of making shoe stiffeners, such asbox toes and counter blanks, carrying a stiffening compound which isadapted to be softened or tempered" by a suitable solvent to permitincorporation in shoes.

A shoe stiffener should be hard, resilient and flexible so that it willimpart to a shoe a maximum degree of firmness and yet not be brittle, sothat it will not crack' upon being bent or indented: A stiffener blankshould adhere to adjacent parts of a shoe to form a unitary structurebut it is imperative that such adhesion be not accompanied by staining.To fit in-the rapid routine of modem shoe manufacture, stiffener blanksmust be adapted to be rendered soft, or tempered, quickly, and when in asoftened condition, they must be capablepof being .wiped over a lastwith little effort on the part of the operator. In order that ashoewillkeep its shape, the stiffening material in a blank should not besoftened by temperatures normally encountered in store windows and wear.Thisresistance to heat conditions has rendered cellulose esterstiffening materials satisfactory because such materials do not becomeplastic at the 25 relatively low temperatures of store windows orencountered in wear.

A stiffener and method of making the same is described and claimed inLovell Patent No. 1,353,- 599. However, there are disadvantagesconnected with the use of present processes, chief among which are firehazard and processing uncertainties. A tremendous fire hazard is presentwhen a bath of dissolved nitrocellulose is used. This solution may beignited by a spark or by the fric- 5 tional heat of moving parts in thedope" or solutionrtank. According to the practice now followed, a baseweb of villous fabric is first coated with a nitrocellulose dope andthen run to a water bath to effect displacement of the nitrocel- 40lulose solvent or solvents. Frequent testing is necessary to determinewhen solvent displacement is complete and this occasions delay andinjects an element of uncertainty .into the process. For the product ofthese processes to be satisfactory, it is essential that a villousbase-web be used so that individual villi will extend through thestiffening material on the surfaces of the web so that in the cutstiffeners these villi will furnish capillary channels or openings forthe penetration of solvent. This type of base, therefore, reduces theamount of time required for tempering. It is important that the villiextend through the coating, for, in the coating apparatus, rolls 55fabric.

are provided for raising the nap or pile on the a It has also beenproposed to treat a web with a suspension of solid cellulose esterparticles in an adhesive paste. With this method, the particles do notpenetrate the body of the web, but merely adhere to the exposed surfacesthereof. As a result, there is notsufiicient stiffening material presentto impart the desired properties to the blank after the temperingoperation.

According to my invention, a cellulose ester stiffening material isused, but the fire hazard is reduced substantially; the need for testingis obviated and the necessity for using a specific type of base fabricto obtain quick tempering is avoided by reason of the physical state ofthe stiffening compound in the finished, treated web. The presentinvention is "directed to a shoe stiffener and method of making the samein which an emulsion of cellulose ester is used. 'The process and theapparatus are simple. A base fabric or web of felt, flannel, or the likeis fed through a bath of emulsified stiffening material and is thendried. This dried web can be cut into stiffeners, such as box toes,which can be skived as is common in the art. The relatively high watercontent of the emulsion reduces the fire risk. No separate water bath isrequired to displace solvent and testing is unnecessary.

In order thatmy invention may be readily understood, I will describe anembodiment and a modification thereof. I have found that a satisfactoryemulsion of stiffening compound can be made by using the followingformula:

Per cent by weight 5 sec. dry nitrocel- Ethyl acetate is thenitrocellulose solvent; and the castor oil is a plasticizer. 23 alcohol(United States Government formula) is ethyl alcohol having a smallpercentage of benzol as a denaturant. The alcohol-and toluol serveasinexpensive diluents of the nitrocellulose solution Duponol, amaterial of commerce, is an emulsifying agent and is produced bysulfonating a fatty alcoholand neutralizing the sulfonated product withso dium hydroxide. The DuponoPand sulfonated castor oil are mixed withwater; and the resulting liquid and the nitrocellulose solutioncontaining the-diluents set forth above are introduced into a suitableemulsifying apparatus to form an movement of solvent from the dispersedphase to the continuous phase. When sufllcient solvent has passed intothe aqueous phase to saturate the same, the solvent, being more volatilethan water, passes from the aqueous phase by surface evaporation. As theaqueous phase loses nitrocellulose solvent, additional solventpasses'from the dispersed nitrocellulose solution into the aqueousphase. It will be evident, therefore, as stated above, that there is acontinuous movement of solvent from the dispersed phase into the aqueousphase, from which it passes by evaporation. J This movement continuesuntil the solvent in the dispersed phase is exhausted. When thisexhaustion stage is reached, the nitrocellulose goes out of solution anddeposits within the body of the web and on.the surfaces thereof in theform of minute, discrete, solid particles. According to priorprocesses,a solution is used, or solid particles are adhesively bonded to thesurface of a web. In the solution process, a film, much in the nature ofa paint film, is formed; and the solvent is displaced in a water bath,leaving a continuous, honeycombed deposit. As stated previously, it isthis continuity of structure which has necessitated the use of a villousfabric to facilitate penetration of solvent. "In the second process, thecellulose ester particles adhere to the faces of the web. In thetempering step, the particles go into solution, which is absorbed by theweb, with the result that there is not sufiicient material-present tostiffen the blank and practicallynone present on the surface to bond theblank in a. shoe upper during the assembling operation. The stifieningcompound in the present product is deposited in the form of discreteparticles within and on the web. Under the action of a solvent, theparticles oi stiffening material go into solution quickly because of theenormous exposed surface area thereof. This solution permeates the baseand, upon evaporation of the solvent, the base becomes stiff because ofthe continuous structure of the stiffening material after the temperingor dissolving step. While in tempered condition, the dissolvednitrocellulose on the surface of the blank allows the box toe blank tobe cemented firmly in the shoe.

With some types of base fabrics, there may be a tendency for thedeposited nitrocellulose stiffening material to be shaken loose from thebase web by rolling, handling and skiving; and I can eliminate thisdusting tendency by using a material which will hold the residue in andon the base web.

For example,1may add rubber latex to the emulsifled stiffening material.Thelatex maybenatural,

The.

to be logical.

synthetic, vulcanized or unvulcanized. I have found that the addition of3.5 parts by weight of 38% latex to parts by weight of emulsioneliminates any tendency toward dusting in the finished product. Latexmixes readily with the emulsion;and, upon drying, the particles ofnitrocellulose are apparently bonded to the base web by a discontinuousrubber film. It has been observed that no dusting occurs, even upontwisting the finished web. It will be apparent, of course, thatmaterials other than latex may be used, such, for example, as casein,dammar gum, waxes and resins. Materials, such as waxes and resins, mayalso be used-as fillers.

The word emulsion" is used herein in its technical sense of denoting acolloidal dispersion of one liquid within another; and aqueous celluloseester emulsion is used herein to define an aqueous emulsion including asolution of a cellulose ester.

The theory of my invention, as set forth above, is based upon myobservation and appears. to me However, I .do not desire to be limitedthereto since further research on the subject may prove such theory tobe incorrect.

While I have described a specific embodiment of my invention, it is tobe understood that this was done for purposes of illustration, and thatthe invention is not so limited but may be otherwise practiced orembodied within the scope of the following claims.

I claim:

1. In the method of making shoe stiifeners, the step of impregnating areadily permeable fibrous web with a water emulsion of minute drops o1!a solution of cellulose ester in a solvent therefor, the solvent beingsoluble to some extent in water and having a lower boiling point thanwater and the water comprising about one-third of the emulsion, andallowing the exhaustion of the solvent to cause deposition of the esteron and within the body of the web in the form of minute, discrete solidparticles.

effective for bonding cellulose ester articles in place within and onthe web, and a owing the exhaustion of the solvent to cause depositionof the ester on and within the body of the web in the form of minute,discrete solid particles bonded within and on the web by said bondingma.- terial.

3. In the method of making shoe stiifeners, the step of impregnating areadily permeable fibrous web with a water emulsion of minute drops of asolution of cellulose ester in a solvent therefor, the solvent beingsoluble to some extent in water and having a lower boiling point thanwater and the-water comprising about one-third of the emulsion," saidimpregnant including rubber latex effective when dried for bondingcellulose ester particles in place within and on the web, and allowingthe exhaustion of the solvent to cause deposition of the ester on andwithin the body of the web in the form of minute, discrete solidparticles bonded within and on the web by the rubber content of saidlatex.

RICHARD ALMY.

emulsion, said impregnant including a material

